http://arxiv.org/abs/2111.07161
One of the goals of the Parker Solar Probe Mission (PSP) is to trace the flow of energy that heats the solar corona and solar wind. The purpose of this paper is to document one achievement of that goal by showing that triggered ion acoustic waves (TIAW) heat the core solar electrons isotropically. TIAW are narrow band ion acoustic waves that (1) appear at frequencies of 200-1000 Hz in shock-like bursts at the few Hz rate of a low frequency ion acoustic-like wave, and (2) that last for hours to days. They contain both electric field and density fluctuations, and they are the dominant wave mode at frequencies greater than 100 Hz at solar distances less than 30 solar radii On PSP orbits 6, 7, 8, and 9, the spacecraft passed through the 22-30 solar radial distance eight times. On two of the passes, there were no TIAW and there was no electron heating. On the remaining six passes, there were TIAW and strong core electron heating. There were also broadband ion acoustic waves on several of the passes and they did not heat the core electrons. The ions were cooler and the solar wind speed was smaller at the times of the TIAW. This resulted in a large core electron to ion temperature ratio, which allowed for the growth of the TIAW. These limited statistics support the conclusion that solar wind core electrons were heated by triggered ion acoustic waves.
F. Mozer, C. Cattell, J. Halekas, et. al.
Tue, 16 Nov 21
72/97
Comments: 12 pages, 6 figures